The present invention relates to a manufacturing method of a light-emitting diode, and more particularly, to a method for manufacturing a diode having excellent light-emitting efficiency at a relatively low temperature.
Currently, lightweight liquid crystal displays having low power consumption are widely in use, however, there are difficulties in obtaining large screen displays and colorization thereof. Due to these limitations in the liquid crystal display, interest in the light-emitting diode (LED) has increased.
In the light-emitting diode, visible rays are emitted when an electric field is applied to the diode, which is a phenomenon called electroluminescence (EL). In the case of a forward bias p/n junction, a hole and an electron are combined near the junction. Here, free electrons of high energy should be able to combine easily with the hole, with emitting energy. In all p/n junction diodes, a part of the energy is emitted in the form of heat or light. Here, the LED uses an emission property of visible light.
The diode essentially comprises a porous silicon layer and a contact layer, in which the material used for the contact layer is a metal, an indium tin oxide (ITO), silicon carbide or a conductive polymer.
Enhanced diodes have a structure in which a p/n junction is provided in the porous region. The porous silicon has the advantage of excellent quantum efficiency, which is defined as the ratio of emitted photons to applied electrons. Also, the light-emitting efficiency of the diode is considerably enhanced when impurities are implanted into the porous layer. For example, a p-type semiconductor is manufactured by doping a group III element such as boron, aluminum, gallium or indium, into the porous silicon in an appropriate ratio, and an n-type semiconductor is manufactured by doping impurities such as phosphorus, arsenic or antimony.
According to the conventional method, the diode having a p/n junction in a porous region is manufactured by forming a p/n junction using implantation or diffusion and then making the p/n junction porous by an appropriate process, or by making a silicon porous and then doping impurities on the porous layer to form a p/n junction.
However, when making the p/n junction porous, the p/n junction is transformed to deteriorate the light-emitting efficiency of the diode. Meanwhile, in the case that impurities are doped into the porous layer, a diffusion or implantation method is used. Here, the diffusion method requires a heat treatment at 900.degree. C. or higher, and the implantation method includes a complicated two-step process.